Rare Appearance of Two Comets in SOHO/LASCO C2 Field of View January 18, 2021.

It is rare to see two comets moving in the SOHO/LASCO C2 Field of View. That occurred on January 18, 2021. In this annotated image, arrows point out the two comets.
The brighter object is a member of the Kreutz group of sun grazing comets. Both objects show tails extending away from the sun. Both comets disintegrated as they approached the solar corona. The head of the brighter comet appears about 4 solar radii from the solar center at position angle 106 degrees. The head of the fainter comet appears about 6 solar radii from the solar center at position angle 223 degrees. The Solar and Heliospheric Observatory (SOHO) is a project of international cooperation between ESA and NASA launched in late 1995.

Karl Battams and Matthew M. Knight, SOHO comets: 20 years and 3000 objects later, Philosophical Transactions of the Royal Society A, Volume 375, Issue 2097, id.20160257 (29 May 2017)


SOHO carries 16 instruments designed to study the Sun from a position that orbits the Earth–Sun L1 Lagrange point. This is beyond the orbital distance of the moon.The LASCO C2 telescope is one of three coronagraph telescopes on SOHO. The LASCO C2 telescope is an externally occulted coronagraph with a field of view extending from approximately 2.0 to 6.4 solar radii.

1 solar radius = 0.00465 AU
Solar diameter = 32 arcminutes

Inner Radius 2 Solar radii
Outer Radius 6.4 Solar radii

“Images are recorded by a 1024×1024 pixel CCD, with a resolution of 11.9 arcsec per pixel. Nominally, C2 images are recorded using a combination of the Orange filter and Clear polarizer. The limiting magnitude for C2 is approximately m9; however, the use of the Orange filter means that this limit is influenced by the colour of the object in question. The majority of SOHO’s comets appear brighter in C2 than in C3, presumed to be due to the strong response of the LASCO Orange filter to sodium emission. “

Published by Charles Bell

The observer at MPC Observatory H47 near Vicksburg, Mississippi, USA

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